. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. Section of shell of Mya arenaria, showing in one part distinct cellular partitions, with large nuclear spots; whilst in another part of the. same layer, the cell- boundaries become fainter, and then disappear alto- gether. Magnified 150 diameters. the section a very distinct set of cell-boun- daries, with a large nuclear spot in the centre of each cell ; whilst on the other side we ob- serve that the cell-walls have completely dis- appeared,—the nuclear spots, however, still remaining to mark the cellular origin of the s
. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. Section of shell of Mya arenaria, showing in one part distinct cellular partitions, with large nuclear spots; whilst in another part of the. same layer, the cell- boundaries become fainter, and then disappear alto- gether. Magnified 150 diameters. the section a very distinct set of cell-boun- daries, with a large nuclear spot in the centre of each cell ; whilst on the other side we ob- serve that the cell-walls have completely dis- appeared,—the nuclear spots, however, still remaining to mark the cellular origin of the substance. A little further on, these also might disappear, and thus all traces of the original organisation might be lost, though no reasonable doubt could be entertained as to its prior existence. A very curious variety of cell-structure is seen in the large hinge-tooth of Mya, in which there is a layer of large cells occupied by carbonate of lime disposed in a radiated form of crystallisation, resembling that of the mineral called Wavellite. Ap- proaches to this beautiful arrangement may be seen in many other shells. Here, too, we find the partitions between the cells gradually becoming less distinct, as we pass from this peculiar stratum into the surrounding substance, until we lose them altogether. In general, a cel- lular layer may be detected upon the external surface of bivalve shells, where this has been pro- tected by a periostracum,or has been prevented in any other mode from undergoing abrasion : Fig. EiVflLUAUS Section of the hinge-tooth of Mya arenaria, showint radiating arrangement of carbonate of lime within the cells, and the gradual disappearance of the cell- boundaries, so that the texture becomes homogeneous. Magnified 80 diameters. Trigonia, Anatina, Solen, Glycimeris, Solemya. &c. In the last-named genus it is very firm, and leaves a distinct membranous residuum after the calcareous matter has been removed by acid, which is not the case with th
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Keywords: ., bo, booksubjectanatomy, booksubjectphysiology, booksubjectzoology
